local mtar = {}

local function cleanPath(path)
 local pt = {}
 for segment in path:gmatch("[^/]+") do
  if segment == ".." then
   pt[#pt] = nil
  elseif segment ~= "." then
   pt[#pt+1] = segment
  end
 end
 return table.concat(pt,"/")
end

function mtar.genHeader(fname,len) -- string number -- string -- generate a header for file *fname* when provided with file length *len*
 return string.format("%s%s%s", string.pack(">I2",fname:len()), fname, string.pack(">I2",len))
end

function mtar.iter(stream) -- table -- function -- Given buffer *stream*, returns an iterator suitable for use with *for* that returns, for each iteration, the file name, a function to read from the file, and the length of the file.
 local remain = 0
 local function read(n)
  local rb = stream:read(math.min(n,remain))
  remain = remain - rb:len()
  return rb
 end
 return function()
  while remain > 0 do
   remain=remain-#stream:read(math.min(remain,2048))
  end
  local nlen = string.unpack(">I2", stream:read(2) or "\0\0")
  if nlen == 0 then
   return
  end
  local name = cleanPath(stream:read(nlen))
  local fsize = string.unpack(">I2", stream:read(2))
  remain = fsize
  return name, read, fsize
 end
end

return mtar